Pros: Very, very pretty.

You can control Nest from cellphones - assuming you replace cellphones every year and always have the latest models with the latest operation system and a plenty of RAM.

You can control Nest from your browser on a desktop or laptop computer (Nest does not let use browser from cellphones for the purpose).

Cons: After working for 3 years, the gizmo suddenly stopped to work in the mid of winter - with no heat provided. Fortunately, the weekend we were at home: otherwise pipes would froze, our basement would be full of water, etc.

The display requested to remove the thermostat from the base and put it back. Next, it kind of started to work: furnace heat on for 25 seconds, followed by a shut down, 2.5 minutes wait, and on again. The loop continued for hours, until an emergency HVAC technician replaced the gizmo by usual, dumb thermostat. I guess that our furnace was not designed to withstand such a loop for long.

I reported it to Nest. They suggested to install the gizmo back, instead of the perfectly fine dumb thermostat, so they can diagnose their product remotely. No way with my furnace!

The failure most likely was caused by firmware that Nest time to time installs remotely. I read later that the night before the failure, Nest pushed out a new firmware release, that should fix bugs in their previous release. In other words, Nest broke a product that worked fine before.

Other Thoughts: The Nest proved to be unsuitable for its purpose.

The design that depends on how well batteries are charged is inherently unsafe. As long as the 24 volt power is provided, thermostat should work with or without a battery.

Updating firmware remotely, without owner participation, also is inherently unsafe.

Thermostats should be completely reliable. Their design should be fail safe: even if bells and whistles fail, they should continue to work as usual, dumb thermostats. They should provide heat in the mid of winter, and they should not attempt to destroy the furnace.

Nest fails to meet these requirements.

Pros: WiFi controlled, can adjust temperature from anywhere.
It's pretty.

Cons: Despite an built in app to know when the sun is shining on it, it can't figure it out. Middle of winter, it thinks its 75 inside when it's actually 55. So now I'm having to turn it up to 80 to get heat. Even on cloudy days, it measures 5-7 degrees hotter than it is.
The learning mode is utterly useless in a professional atmosphere...even at home. Ultimately, I used more electricity with the Nest than a normal thermostat. It changes randomly and sometimes without reason. If I decide that I no longer want the same temperature I did last week, I have to reprogram the schedule. Even on the phone, it's a hassle and takes a long time. I can't imagine how hard a time my parents would have with this.

Other Thoughts: Get a HW smart thermostat, set up your own schedule. They are prettier, cheaper, and more functional. Honestly, I own two of these. One at home, one at work, and my parents got one too. I have changed my thermostats back to the old manual variety and my parents regret the Nest as well. Save your money for your electric bill.

Pros: Looks nice, easy to change temperatures quickly.

Cons: This device is terrible and a SCAM. First of all, it has a mind of its own, changing the temperature on me in the middle of the night and creating new adjustments completely outside of the schedule I made. But now it's the end of the line. The Nest NO LONGER WORKS. There is first the "battery drain" issue, where the thermostat has to be removed from the base, be charged for SEVERAL HOURS by microUSB, and then but back on the base to turn on. But the bigger issue is that it DOESNT HEAT OR COOL ANYMORE. I will set a temperature and it shows that heater or AC are on but nothing happens. I had an HVAC guy come and he diagnosed that it is 100% due to the thermostat. I have tried calling and emailing Nest and have gotten NO RESPONSE. I am done with Nest and will be leaving this review on every website that Nest is sold.

Pros: Great for anyone as it learns your habits
If you want you can be hands off,
If you are like me you can get hour by hour and daily usage stats.
Looks great, setup is a breeze
Can control it from my smartphone

Cons: Pricey and don't often go on sale. I was lucky as there was a $50 GC to Newegg and a $10 rebate from my electric company which took out some of the sting

Other Thoughts: would definitely recommend and would buy again.

Pros: Nice design. east set up. 150 dollars CPS reward!!

Cons: nothing so far.

Other Thoughts: It took 5 minutes to install on old setup. I worried about the wires before receiving this product, but installing was so smooth and easy.

Pros: Easy and quick installation. Works well. The auto-away, remote access via the app, and schedules will save me some coin this winter in heating bills.

Cons: Still a little costly, other than that I can't think of any yet.

Other Thoughts: Would recommend.

Pros: Very easy to setup. Picks up internet easily. So far, so good, works as advertised.

Cons: No native app for Windows phone. Shell app created by a third party and free on app store works, but can't see everything on screen. Nest needs to fix this.

Pros: Slick, controllable from the app, gives you some stats, connects with IFTTT.

Cons: Price, and many limitations.
For example, only allows you to configure 2 separate homes from one account, which creates a big problem especially when paired with fire alarm.
Most probably, setup will require at least 3 wire system or it will have battery charging problems.
Constant disconnects from wi-fi even within a few feet of the router, although after firmware update it does reconnect itself, just not right away.
Another annoying thing is +-1 degree temperature regulation. This is extremely annoying, since it may not trigger the thermostat for hours. Depending on the outside temperature, your house setup and if one thermostat controls more than one room you may be uncomfortable.

Other Thoughts: Although I have a v2, most of the comments will still apply to v3.
Make sure to do good research before wasting money.

Pros: Pays for itself. Easily managed.

Cons: Price?